Method of removing scale oxid from the surface of iron or steel.



252. COMPOSITIONS,

I ear [G h .irso s rn'rns 3- PATENT OFFICE.

METHOD OF REMOVING SCALE OXID FROM THE SURFACE OF IRON 0R STEEL.

SPECIFICATION runningpart of Letters Patent No. 702,050, dated June 10,1902.

I I Application filed September 10, 1900. Serial No. 29,547.(No'speclmena) To all whom it may concern:

Be it known that I, ASAHEL K. EATON, of the borough of Brooklyn, countyof Kings, and State of New York, have invented a new 5 and useful Methodof Removing Scale Oxid from the Surface of Iron or Steel; and I herebydeclare that the following is such a clear, full, and exact descriptionof the same as will enable those skilled in the art to which my in- 110vention pertains to use or practice the same.

In the removal of ha mmerascale, as it is called, from the surfacf ofhammered or rolled iron or steel it has been customary to use.

lstrong corrosive acids, such 'ssulfuric, hy- "I5drochloric,' the. Theseacids efiect the de;'-

sired result at the expense, largely, of the underlying pure metal.This'is especially so in the treatment of the lighter articles of iron Iand steel, such as wire br thin .plate. The

acid acts injuriously by the dissolving of the metal and consequent-loss thereof, and by molecular change of structure causes a brittlenessand loss of thatelasticity and toughness which the metal exhibitedbefore treatment. I therefore sought. for a substitute that would attackthe mid only, leaving the underlying pure metal intact. I finallyreached a satisfactory solution of the problem, which I will heredescribe.

The scale oxid found upon thesurface of all rolled or hammered iron orsteel is represented by 'the chemical formulae FeO and Fe O thatis tosay, a mixtu re,varyin gin different cases, of the protoxid andsesquipxjd of iron. It was desirable to find a compound which wouldreadily dissolve these oxids without attacking the underlying surface.In eflfecting this 'it was necessary to devise a chemical combinationwhich by first reducing the Fe O to the protoxid made the whole scaleeasily soluble, with the qualification that the solution or combinationshould be entirely neutral to the metallic surface beneath. I p

The agents which I have found to be most efficacious in carrying out myprocess are so lutions of sodium bisulfate and stannops chlorjd.Thsi'm'plest'afid"most economical m'dtlnod of producing this mixture Ihave found to be as follows I dissolve one hundred parts of sodiumbisulfale in five hundred parts of water and tdthis add a solution oftwo parts 5551111 115 chlorid in thre parts of water. The result of thiscombination is by double decomposition a fluid consisting mostly ofdissolved sodium bisulfate and a small portion of stannoussiilfa'tbrwhich acts as'a reuuclm a cut of them hi 1" lzenso t esca e.epresented y cermc'a ormu ae,the reaction resultingfrom the mi re of thesodium bisulfate and the stann s chlorid isform of a protosalt, being anexcellent 1;e

duciug agent, resolves the Fe,0,, constituent DRAFISMAN.

otthe sca e to FeO, thTareby rendering the I whole of the scaleconipletely soluble in the extra acid constituent of the bi-acid salt. A

desirable feature connect''diviththis reaction is that while thesolution of sodium'bi- 4, sulfate readily attacks the scale when thusreduced it has no pe cep f y or the ,1

bared metal. In order to prove this, I removed the scale of some thinsteel, dried and weighed the metal,.and"then for three days left it inthe solution. it was then dried and I weighed again, and I form 0appreciable loss of weight. w I The time required in a cold fre solution0 r hour. If the solution be heated, the time T: will be shortened toabout five minutes.

for the removal of the scale is about half an The cold solution afterbeing weakened by use requires a relatively. longer time or more or lessheat to produce the same action in the same time; When the solutionbecomes weak, it may be improved by putting scraps of bright tin intothe bath.

The same results could be obtained by the substitution of potas s i uin. bisulfate for, the

sodium salt; but the cost of this would be practically prohibitive. aThe sodium bisulfate will by itself to a cer 2 a g 702,050 I tain degreeremove the oxid; but as it attacks readily the protoxid constituent onlyit is not sufficiently rapid in its action.

Having now described my invention, what I claim is- 1. The method hereindescribed of removing hammer-scale from iron or steel, which consists intreating the same with an agent to reduce the more insoluble ox'ids ofthe scale to a soluble condition, and with a solvent for the resultingoxid which does not injuriously attack the underlying metal, as setforth.

2. The method herein described of removing hammer-scale from iron orsteel, which consists in subjecting the same to the simultaneous actionof a reducing agent for the higher oxids, and a solvent of the loweroxids, in the form of a mikture of the solutions of the two agents, asset forth.

3. The method herein described of remov- 2o ing hammer-scale from ironor steel, which consists in immersing the iron in a bath containing areducing agent for the higher oxids, and sodium bisulfate, as set forth.

4. The method herein described of removing hammer-scale from iron orsteel, which consists in treating the same with a. bath containing insolution stannous sulfate and sodinm bisulfat-e, as set forth.

5. The method herein described of removing hammer-scale from iron orsteel, which consists in subjecting the scale-coated metal to the actionof a bath containing sodium bisulfate, as set forth.

A. K. EATON.

Witnesses: L. 0. SHERWOOD,

H. M. EATON.

